Swaged fittings have been used for many years to connect tubes and pipes in various types of fluid systems, including those used in the aircraft, marine, petroleum and chemical industries. A tube end is inserted into a fitting, usually in the form of a cylindrical sleeve, and then the fitting is swaged with a swaging tool to produce a fluid-tight connection around the tube. This swaging operation usually is carried out by applying a radial force which radially compresses the fitting and tubing inwardly. This radial force may be applied directly by the swaging tool or indirectly by a specially shaped ring which is moved axially by the swaging tool to apply a radial force to the fitting. The invention of the present application is directed to the latter type of swaging tool designed for use with fittings having axially movable swaging rings. These fittings shall be referred to as axially swaged fittings.
Typical axially swaged fittings comprise a cylindrical sleeve having openings at opposite ends for receiving the ends of two tubes to be connected, with a swaging ring at each end of the sleeve. The outer surface of the sleeve and the inner surface of the swaging ring which contact each other are shaped such that axial movement of the swaging ring over the sleeve applies a radial force to the sleeve and, thus, to the tubes. Although not all fittings employ a sleeve with two swaging rings, the use of two swaging rings is necessary when it is desired, as is often the case, to join two tubes to each other.
One type of swaging tool for axially swaged fittings is described in U.S. Pat. No. 5,398,394 issued on Mar. 21, 1995, which is incorporated herein by reference. The tool includes a housing having an inner surface and an outer surface, and a piston that is movable in opposite axial directions within the housing. The piston has a cylindrical outer surface in axial sliding engagement with the inner surface of the housing. The housing has a closed end and an open end. The open end is threaded and connected to a threaded cap, which encloses the piston within the housing. The cap is connected to a source of hydraulic pressure for selectively moving the piston axially within the housing. A first engaging member is formed on the outer surface of the housing adjacent to the closed end for engaging one of the ring or the sleeve of the fitting to restrain it from axial movement. A second engaging member is formed on the outer surface of the piston for engaging the other one of the ring or the sleeve to move it in an axial direction toward the first engaging member upon movement of the piston toward the closed end of the housing.
While the above-described swaging tool works quite well, it does have its disadvantages. In particular, the housing is slotted to accommodate axial movement of the piston and second engaging member. Therefore, additional parts, such as a support ring to support the threaded end of the housing during swaging, are often necessary to maintain the structural integrity of the swaging tool. Also, the threaded cap requires occasional tightening, which increases the maintenance requirements of the device.
Another type of axial swaging tool is described in U.S. Pat. No. 4,189,817 to Moebius. This tool also includes a housing having a cylinder that receives a piston. A screw threaded end closure having a pressure fluid inlet closes the end of the cylinder. A movable jaw unit is received on a guide shaft extending axially from the piston and a fixed jaw unit is mounted to the housing in confronting relationship to the movable jaw unit. A slide arm mounted to the movable jaw unit extends parallel to the cylinder and engages a longitudinal bearing surface on the outside of the cylinder to counteract deflection of the movable jaw unit during a swaging operation. The location of the slide arm along the outside of the cylinder, however, actually aggravates the deflection problem because it significantly increases the distance between the force generating axis (i.e., the piston axis) and the force application axis (i.e., the fitting axis), which, in turn, increases the bending moment on the movable jaw. In addition, as with the swaging tool described above, the threaded end cap requires occasional tightening and therefore increased maintenance of the tool.
Another axial swaging tool is described in U.S. Pat. No. 5,305,510 to Croft et al. In this tool, the hydraulic cylinder appears to be capless. Therefore, it would not have the maintenance requirements described in connection with the above devices. However, in this case, the movable jaw unit is mounted to the piston by a threaded fastener, which itself requires tightening. In addition, the movable jaw unit includes a pad that extends parallel to the cylinder and engages a longitudinal bearing surface on the outside of the cylinder. This pad, like the slide arm in the Moebius patent, increases the bending moment on the movable jaw because it increases the distance between the piston axis and the fitting axis.
A further axial swage tool is described in U.S. Pat. No. 4,345,361 to Baumann, which appears to show another capless hydraulic cylinder. It is unclear, however, how the tool is assembled.
In view of the above, it should be appreciated that there is still a need for an axial swaging tool that has fewer maintenance requirements, is lighter in weight, and is more reliable in service. The present invention satisfies these and other needs and provides further related advantages.